a lot has been covered in the post already. If your shooting quarter sized groups at 15 yards - push yourself faster - but don't violate the fundamentals

fast accurate shooting is the fundamentals done quickly.

DRY FIRE ( a lot) but dry fire with discipline - don't just bring the gun up and pull the trigger - consciously acquire that front site and and discipline yourself to get that additional site picture before bringing it down - your shot sequence ends on an additional sight picture - period

and OF COURSE you aim in a combat situation - instinctive fire (looking at where you want it to hit) is for close in shooting (under 7m or imho under 5m) Use that flash sight picture . (see DRY FIRE)